textproduct: Rapid City

KEY MESSAGES

- Severe thunderstorm risk across south central SD this afternoon and evening with large hail and damaging winds as the primary threats, though a tornado can't be ruled out.

- Chance of severe weather with all hazards possible Thursday.

- Warming temperatures expected into the weekend.

DISCUSSION

(This Evening Through Wednesday) Issued at 1250 PM MDT Wed Jun 3 2026

Visible satellite shows cloud cover over much of western SD with ongoing storms over north central SD. Skies have cleared out over Wyoming and the Black Hills with water vapor imagery showing narrow plume of mid level moisture streaming into south central SD. Sfc cold front makes its way across the eastern tier of the CWA through this afternoon and evening. Plume of 50-60F dewpoints and moderate instability of 2000-3000 J/kg SB CAPE will support thunderstorm development along the front. Mid-level flow will strengthen as the shortwave approaches with deep layer shear increasing to 30-40 kts which will support organized convection and rotating updrafts. CAMs are once again struggling with timing and storm mode with the HRRR continuing to push back development over south central SD until later this evening (after 6 to 7 pm) while the NAM and RRFS both show storms developing somewhat earlier (around the 4 to 5 pm MDT timeframe). Storms may start off as discrete cells, capable of large hail, damaging winds, and a low tornado risk. Storms will quickly coalesce into a line as the front pushes through with the primary threat transitioning to damaging wind gusts.

Attention turns to tomorrow where severe thunderstorms are once again possible across much of the forecast area. Another shortwave moving along nearly zonal flow will eject over the Northern Plains by the afternoon hours. Strengthening mid level flow will support deep layer shear values of 30 to 40 kts with SBCAPE values climbing to 2000-3000+ J/kg with the highest values across southwestern SD. This looks to be a typical northern Black Hills supercell environment, capable of very large hail (2+"), though a tornado or two can't be entirely ruled out. As storms push eastward over the plains through the evening hours, they may transition into an MCS with associated severe wind threat.

Things settle down for most of the CWA Friday as shortwave ridging builds to our west. Storms are still possible over south- central SD as the sfc front and shortwave exit the region. In addition, diurnally driven showers can't be ruled out over the Black Hills in the afternoon. Shortwave ridge will move over the region by Saturday and bring hot and dry conditions to the CWA. Storm chances return Sunday as upper level trof deepens over the western US and places our CWA under unsettled southwest flow.

AVIATION

(For the 00Z TAFS Through 00Z Thursday Evening) Issued At 707 PM MDT Wed Jun 3 2026

Light, moist easterly flow up against the Black Hills tonight into Thursday morning may support some form of low stratus and/or fog across portions of the South Dakota plains, especially between 10-16z/4-10am (broadly-speaking). Not all models agree and they don't advertise great coverage overall, but enough support exists that we did include MVFR low stratus for KRAP starting at 11z/5am locally. Fog would be even more impactful, but confidence remains very low. Thursday afternoon, conditions then become favorable for isolated to scattered, potentially severe thunderstorms to develop over the Black Hills corridor, and possibly across northeastern Wyoming as well. A great deal of disagreement exists among the CAMs on timing, but have added PROB30 groups to both KGCC and KRAP for this activity with a slightly earlier start time at KRAP due to the nearby terrain assisting with convective initiation. Storms could produce large hail and damaging winds, along with at least MVFR if not IFR conditions for brief periods near/under cores as storms spread eastward into the South Dakota plains during the evening.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.